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Twelve lactating sows were used to evaluate the effects of reducing dietary crude protein ( CP) (14% vs. 12%) and increasing neutral detergent fibre ( NDF) levels (18% vs. 22%) on litter performance, total tract apparent digestibility and manure composition in a 4 × 4 latin square arrangement during a 36-day lactation period. Diets were isoenergetic (2.9 Mcal ME/kg) and had similar total lysine content (0.9%). In addition, a second aim was to compare a reference external marker method (Cr2O3) with an internal feed marker [acid-insoluble ash ( AIA)] for the calculation of apparent total tract digestibility of nutrients in lactating sows. The reduction of dietary CP level in lactating sows had no effect on either live-weight or backfat thickness or apparent total tract digestibility of nutrients. However, the piglets' average daily gain ( ADG) was reduced in low dietary CP diets, which suggests that sows reduced milk production due to an underestimation of certain essential amino acid requirements (e.g. valine). The increase of dietary NDF level did not affect sow and litter performance. Nevertheless, the total tract apparent digestibility of organic matter, CP and carbohydrates was reduced, and ether extract digestion was increased in high NDF compared to normal NDF diets equally balanced for ME and lysine content. The coefficients of total tract apparent digestibility of nutrients in lactating sows were greater when using AIA compared to Cr2O3 marker, regardless of dietary CP or NDF level, but their coefficients of variation were lower in the former than in the latter. In lactating sows, a trade-off between litter performance and nutrient digestion is established when reducing dietary CP or increasing NDF levels while maintaining similar lysine content through synthetic amino acids and balancing metabolizable energy through dietary fat sources. [ABSTRACT FROM AUTHOR]

This study evaluated the carry-over effects of ewe body reserves during early pregnancy on peri-partum adipose tissue metabolism. Forty-nine multiparous ewes were divided in three categories according to their body condition score (BCS) at day 30 of pregnancy (BCS < 3, 2.5-2.75; BCS = 3; BCS > 3, 3.25-3.5). Live-weight (LW) and BCS gains from 1st to 4th month of pregnancy were greater in ewes with BCS < 3 and 3 than in >3 animals. In contrast, in the last month of pregnancy, there was BCS decrease in all groups, although LW continued increasing. There were no differences in LW or BCS across ewe categories during this period. Peripheral leptin levels throughout the three last weeks of pregnancy were greater in ewes with BCS > 3 than in the rest, but this difference did not persist after lambing. Plasma metabolites related to energy metabolism, milk yield and lamb growth were not affected by ewe BCS in early pregnancy. Long-chain saturated milk fatty acids (FA) (C16-C24) were greater in ewes with lowest BCS (<3 and 3). Ewes with greater BCS showed greater monounsaturated and lowest polyunsaturated milk FA content. Ewe post-mating body reserves affect both pre-partum leptinaemia and post-partum milk polyunsaturated fatty acids content, but it had little effect on lamb performance. [ABSTRACT FROM AUTHOR]

The episodic release of luteinizing hormone (LH) and growth hormones (GH) was studied in three suckling regimens and two breeds of Spanish suckled cows. Parda de Montaña (PA) cows ( n = 21) were assigned to once-daily, twice-daily or ad libitum (ADLIB) suckling. Pirenaica (PI) cows ( n = 7) were used to evaluate the breed effect in twice-daily suckling. Coccygeal blood samples were collected twice weekly during lactation to determine the interval from calving to first ovulation through peripheral progesterone. On day 32 ± 3 post-partum, jugular blood samples were drawn at 15 min intervals during 8 h to analyse circulating LH and GH. The interval to first ovulation was greater in PA cows suckling ADLIB than in restricted suckling treatment (RESTR1), whereas in RESTR2 it did not differ from the other two treatments. There were no differences between PA and PI cows in the interval to first ovulation. RESTR1 cows showed a tendency to have shorter LH peak widths than ADLIB cows. PA cows showed a tendency to have longer LH peak widths than their PI counterparts. There were no differences across treatments or breeds in any of the GH measures of secretion. The LH release was more affected by breed than by suckling frequency, whereas that of GH was not influenced by any of these parameters. The variables that best allowed discrimination between ADLIB and restricted nursing systems were the interval to post-partum first ovulation, LH peak number and the mean GH concentration. [ABSTRACT FROM AUTHOR]

This experiment aimed at evaluating the effect of calf management and breed on the metabolic and luteal function of post-partum beef cows fed at maintenance. Fifty multiparous cows, 22 Parda de Montaña (PA) and 28 Pirenaica (PI), were assigned to either suckling once-daily for 30 min (RESTR) or ad libitum (ADLIB) from the day after calving. Blood samples were collected to analyse metabolites [non-esterified fatty acids (NEFA), β-hydroxybutyrate, total protein and urea)], insulin-like growth factor-I (IGF-I) and progesterone (P4) at different intervals. Cows from RESTR maintained their live-weight (LW) over the first 3 months post-partum, whereas ADLIB cows lost nearly 4% LW. Both genotypes showed similar LW gains during this period (p > 0.10). Calf daily gains were lower in RESTR than in ADLIB treatment (p < 0.05), but similar across breeds (p > 0.10). Milk and lactose production were lower in RESTR cows than in ADLIB (p < 0.05). Milk and protein yield were greater in PA than in PI breed (p < 0.05). Serum NEFA, total protein and urea were higher in PI cows suckling ADLIB than in the rest (p < 0.05). Cows from PI breed had greater NEFA values than PA ones on the first week post-partum (p < 0.001). Circulating IGF-I was not affected by suckling frequency, breed nor their interaction (p > 0.10). Suckling frequency, but not breed, affected the interval from calving to first ovulation (p < 0.001), being shorter in RESTR than in ADLIB cows. In conclusion, the ad libitum suckling practice improved cow milk yield and offspring gain compared to once-daily suckling for 30 min from the day after calving, at the expense of impairing the onset of cyclicity. The effect of calf management was confounded with breed on the studied blood biochemical constituents, but any of these metabolites influenced the role of endocrine IGF-I in these genotypes. [ABSTRACT FROM AUTHOR]